code: def test_get_returns_none_when_not_found(self):
      self.override_dict.set_base("a", 42)
  
      self.assertEqual(self.override_dict.get("nonexistent_key"), None)
  
imports: from typing import Sequence
  from torch.onnx import errors
  from torch.onnx._internal import registration
  from torch.testing._internal import common_utils
label_desc: Use image node_id 6 for calling the TestOverrideDict obj's underlying member method code with example usage: obj.test_get_returns_none_when_not_found() without return types